Two piece cancellous construct for cartilage repair

ABSTRACT

The invention is directed toward a cartilage repair assembly comprising a shaped allograft two piece construct with a demineralized cancellous cap and a mineralized cylindrical base member defining a blind bore with a through going transverse bore intersecting the blind bore. The demineralized cancellous cap has a cylindrical top portion and a smaller diameter cylindrical stem extending away from the top portion which fits into the blind bore of the mineralized base member. The cap stem defines a transverse through going bore which is aligned with the through going bore of the base member to receive a cylindrical cortical pin holding the cap within the base member. The shaped structure is dimensioned to fit in a drilled bore in a cartilage defect area so that the assembly engages the side wall of the drilled bore in an interference fit.

RELATED APPLICATIONS

There is no related application.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO SEQUENCE LISTING, A TABLE OR A COMPUTER PROGRAM LISTINGCOMPACT DISC APPENDIX

None.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention is generally directed toward an allograftcartilage repair implant and is more specifically directed toward a twopiece allograft cancellous bone implant having a demineralizedcancellous bone cap member and a mineralized or partially demineralizedcancellous bone base member, both pieces being held together with anallograft bone pin. The construct is shaped for an interference fitimplantation in a shoulder, knee, hip, or ankle joint. The base memberis provided with an axially positioned blind bore and a plurality ofsmaller diameter through going bores which allow transport of cellularmaterials throughout the implant site to stimulate cartilage growth

2. Description of the Prior Art

Articular cartilage injury and degeneration present medical problems tothe general population which is constantly addressed by orthopedicsurgeons. Every year in the United States, over 500,000 arthroplastic orjoint repair procedures are performed. These include approximately125,000 total hip and 150,000 total knee arthroplastics and over 41,000open arthroscopic procedure to repair cartilaginous defects of the knee.

In the knee joint, the articular cartilage tissue forms a lining whichfaces the joint cavity on one side and is linked to the subehondral boneplate by a narrow layer of calcified cartilage tissue on the other.Articular cartilage (hyaline cartilage) consists primarily ofextracellular matrix with a sparse population of chondrocytesdistributed throughout the tissue. Articular cartilage is composed ofchondrocytes, type II collagen fibril meshwork, proteoglycans and water.Active chondrocytes are unique in that they have a relatively lowturnover rate and are sparsely distributed within the surroundingmatrix. The collagens give the tissue its form and tensile strength andthe interaction of proteoglycans with water give the tissue itsstiffness to compression, resilience and durability. The hyalinecartilage provides a low friction bearing surface over the bony parts ofthe joint. If the lining becomes worn or damaged resulting in lesions,joint movement may be painful or severely restricted. Whereas damagedbone typically can regenerate successfully, hyaline cartilageregeneration is quite limited because of it's limited regenerative andreparative abilities.

Articular cartilage lesions generally do not heal, or heal onlypartially under certain biological conditions due to the lack of nerves,blood vessels and a lymphatic system. The limited reparativecapabilities of hyaline cartilage usually results in the generation ofrepair tissue that lacks the structure and biomechanical properties ofnormal cartilage. Generally, the healing of the defect results in afibrocartilaginous repair tissue that lacks the structure and biomedicalproperties of hyaline cartilage and degrades over the course of time.Articular cartilage lesions are frequently associated with disabilityand with symptoms such adjoint pain, locking phenomena and reduced ordisturbed function. These lesions are difficult to treat because of thedistinctive structure and function of hyaline cartilage. Such lesionsare believed to progress to severe forms of osteoarthritis.Osteoarthritis is the leading cause of disability and impairment inmiddle-aged and older individuals, entailing significant economic,social and psychological costs. Each year, osteoarthritis accounts foras many as 39 million physician visits and more than 500,000hospitalizations. By the year 2020, arthritis is expected to affectalmost 60 million persons in the United States and to limit the activityof 11.6 million persons.

There are many current therapeutic methods being used. None of thesetherapies has resulted in the successful regeneration of hyaline-liketissue that withstands normal joint loading and activity over prolongedperiods. Currently, the techniques most widely utilized clinically forcartilage defects and degeneration are not articular cartilagesubstitution procedures, but rather lavage, arthroscopic debridement,and repair stimulation. The direct transplantation of cells or tissueinto a defect and the replacement of the defect with biologic orsynthetic substitutions presently accounts for only a small percentageof surgical interventions. The optimum surgical goal is to replace thedefects with cartilage-like substitutes so as to provide pain relief,reduce effusions and inflammation, restore function, reduce disabilityand postpone or alleviate the need for prosthetic replacement.

Lavage and arthroscopic debridement involve irrigation of the joint withsolutions of sodium chloride, Ringer or Ringer and lactate. Thetemporary pain relief is believed to result from removing degenerativecartilage debris, proteolytic enzymes and inflammatory mediators. Thesetechniques provide temporary pain relief, but have little or nopotential for further healing.

Repair stimulation is conducted by means of drilling, abrasionarthroplasty or microfracture. Penetration into the subchondral boneinduces bleeding and fibrin clot formation which promotes initialrepair, however, the tissue formed is fibrous in nature and not durable.Pain relief is temporary as the tissue exhibits degeneration, loss ofresilience, stiffness and wear characteristics over time.

The periosteum and perichondrium have been shown to contain mesenchymalprogenitor cells capable of differentiation and proliferation. They havebeen used as grafts in both animal and human models to repair articulardefects. Few patients over 40 years of age obtain good clinical results,which most likely reflect the decreasing population of osteochondralprogenitor cells with increasing age. There have also been problems withadhesion and stability of the grafts, which result in their displacementor loss from the repair site.

Transplantation of cells grown in culture provides another method ofintroducing a new cell population into chondral and osteochondraldefects. CARTICELl® is a commercial process to culture a patient's owncartilage cells for use in the repair of cartilage defects in thefemoral condyle marketed by Genzyme Biosurgery in the United States andEurope. The procedure uses arthroscopy to take a biopsy from a healthy,less loaded area of articular cartilage. Enzymatic digestion of theharvested tissue releases the cells that are sent to a laboratory wherethey are grown for a period ranging from 2-5 weeks. Once cultivated, thecells are injected during a more open and extensive knee procedure intoareas of defective cartilage where it is hoped that they will facilitatethe repair of damaged tissue. An autologous periosteal flap with acambium layer is used to seal the transplanted cells in place and act asa mechanical barrier. Fibrin glue is used to seal the edges of the flap.This technique preserves the subchondral bone plate and has reported ahigh success rate. Proponents of this procedure report that it producessatisfactory results, including the ability to return to demandingphysical activities, in more than 90% of patients and those biopsyspecimens of the tissue in the graft sites show hyaline-like cartilagerepair. More work is needed to assess the function and durability of thenew tissue and determine whether it improves joint function and delaysor prevents joint degeneration. As with the perichondrial graft,patient/donor age may compromise the success of this procedure aschondrocyte population decreases with increasing age. Disadvantages tothis procedure include the need for two separate surgical procedures,potential damage to surrounding cartilage when the periosteal patch issutured in place, the requirement of demanding microsurgical techniques,and the expensive cost of the procedure which is currently not coveredby insurance.

Osteochondral transplantation or mosaicplasty involves excising allinjured or unstable tissue from the articular defect and creatingcylindrical holes in the base of the defect and underlying bone. Theseholes are filled with autologous cylindrical plugs of healthy cartilageand bone in a mosaic fashion. The osteochondral plugs are harvested froma lower weight-bearing area of lesser importance in the same joint. Thistechnique, shown in Prior Art FIG. 2, can be performed as arthroscopicor open procedures. Reports of results of osteochondral plug autograftsin a small numbers of patients indicate that they decrease pain andimprove joint function, however, long-term results have not beenreported. Factors that can compromise the results include donor sitemorbidity, effects of joint incongruity on the opposing surface of thedonor site, damage to the chondrocytes at the articular margins of thedonor and recipient sites during preparation and implantation, andcollapse or settling of the graft over time. The limited availability ofsites for harvest of osteochondral autografts restricts the use of thisapproach to treatment of relatively small articular defects and thehealing of the chondral portion of the autograft to the adjacentarticular cartilage remains a concern.

Transplantation of large allografts of bone and overlying articularcartilage is another treatment option that involves a greater area thanis suitable for autologous cylindrical plugs, as well as for anon-contained defect. The advantages of osteochondral allografts are thepotential to restore the anatomic contour of the joint, lack ofmorbidity related to graft harvesting, greater availability thanautografts and the ability to prepare allografts in any size toreconstruct large defects. Clinical experience with fresh and frozenosteochondral allografts shows that these grafts can decrease jointpain, and that the osseous portion of an allograft can heal to the hostbone and the chondral portion can function as an articular surface.Drawbacks associated with this methodology in the clinical situationinclude the scarcity of fresh donor material and problems connected withthe handling and storage of frozen tissue. Fresh allografts carry therisk of immune response or disease transmission. MusculoskeletalTransplant Foundation (MTF) has preserved fresh allografts in a mediathat maintains a cell viability of 50% for 35 days for use as implants.Frozen allografts lack cell viability and have shown a decreased amountof proteoglycan content which contribute to deterioration of the tissue.

A number of United States Patents have been specifically directedtowards bone plugs which are implanted into a bone defect. Examples ofsuch bone plugs are U.S. Pat. No. 4,950,296 issued Aug. 21, 1990 whichdiscloses a bone graft device comprising a cortical shell having aselected outer shape and a cavity formed therein for receiving acancellous plug, which is fitted into the cavity in a manner to exposeat least one surface; U.S. Pat. No. 6,039,762 issued Mar. 21, 2000discloses a cylindrical shell with an interior body of deactivated bonematerial and U.S. Pat. No. 6,398,811 issued Jun. 4, 2002 directed towarda bone spacer which has a cylindrical cortical bone plug with aninternal through going bore designed to hold a reinforcing member. U.S.Pat. No. 6,383,211 issued May 7, 2002 discloses an invertebral implanthaving a substantially cylindrical body with a through going boredimensioned to receive bone growth materials.

U.S. Pat. No. 6,379,385 issued Apr. 30, 2002 discloses an implant basebody of spongious bone material into which a load carrying supportelement is embedded. The support element can take the shape of adiagonal cross or a plurality of cylindrical pins. See also, U.S. Pat.No. 6,294,187 issued Sep. 25, 2001 which is directed to a load bearingosteoimplant made of compressed bone particles in the form of acylinder. The cylinder is provided with a plurality of through goingbores to promote blood flow through the osteoimplant or to hold ademineralized bone and glycerol paste mixture. U.S. Pat. No. 6,096,081issued Aug. 1, 2000 shows a bone dowel with a cortical end cap or capsat both ends, a brittle cancellous body and a through going bore.

While these implants have been used for bone tissue regeneration, thesame will not work to repair cartilage areas due to the osteoinductivenature of the bone which causes bone growth.

The use of implants for cartilage defects is much more limited. Asidefrom the fresh allograft implants and autologous implants, U.S. Pat. No.6,110,209 issued Nov. 5, 1998 shows the use an autologous articularcartilage cancellous bone paste to fill arthritic defects. The surgicaltechnique is arthroscopic and includes debriding (shaving away loose orfragmented articular cartilage), followed by morselizing the base of thearthritic defect with an awl until bleeding occurs. An osteochondralgraft is then harvested from the inner rim of the intercondylar notchusing a trephine. The graft is then morselized in a bone graft crusher,mixing the articular cartilage with the cancellous bone. The paste isthen pushed into the defect and secured by the adhesive properties ofthe bleeding bone. The paste can also be mixed with a cartilagestimulating factor, a plurality of cells, or a biological glue. Allpatients are kept non-weight bearing for four weeks and used acontinuous passive motion machine for six hours each night. Histologicappearance of the biopsies has mainly shown a mixture of fibrocartilagewith hyaline cartilage. Concerns associated with this method are harvestsite morbidity and availability, similar to the mosaicplasty method.

U.S. Pat. No. 6,379,367 issued Apr. 30, 2002 discloses a plug with abase membrane, a control plug, and a top membrane which overlies thesurface of the cartilage covering the defective area of the joint.

SUMMARY OF THE INVENTION

A cartilage repair allograft construct implant comprising a two pieceallograft bone construct with a mineralized cylindrical cancellous bonebase member and a demineralized and non-osteoinductive cancellous bonecap member mounted in a blind bore cut in the cancellous bone basemember, the two members being held together by an allograft bone pin.The two piece construct is used for replacing articular cartilagedefects and is placed in a bore which has been cut into the patient toremove the lesion defect area. The bone base member has an axiallyaligned blind bore, a transverse through going bore which intersects theblind bore and has a plurality of through going bores which run parallelto the axis of the cylindrical bone base member. The cap member has astem which fits into the blind bore of the base member with the stemdefining a transverse through going bore. The base surface of the capmember body overlies the upper surface of the cylindrical base memberwith the stem bore and the base member transverse bore being aligned toreceive a cortical pin. Additives may be applied to the internal bores,blind bore or the cap member of the construct in order to increase oraccelerate cartilaginous or bony tissue formation Each allograftconstruct can support the addition of a variety of chondrogenicstimulating factors including, but not limited to morselized allogeneiccartilage, growth factors (FGF-2, FGF-5, IGF-1, TGF-β, BMP-2, BMP-7,PDGF, VEGF), human allogenic or autologous chondrocytes, human allogenicor autologous bone marrow cells, stem cells, demnineralized bone matrix,insulin, insulin-like growth factor-1, transforming growth factor-B,interleukin-1 receptor antagonist, hepatocyte growth factor,platelet-derived growth factor, Indian hedgehog and parathyroidhormone-related peptide or bioactive glue.

It is an object of the invention to provide an allograft implant forjoints which provides pain relief, restores normal function and willpostpone or alleviate the need for prosthetic replacement.

It is also an object of the invention to provide a cartilage repairimplant which is easily placed in a defect area by the surgeon using anarthroscopic, minimally invasive technique.

It is still another object of the invention to provide an allograftimplant which has load bearing capabilities.

It is further an object of the invention to provide an allograft implantprocedure which is applicable for both partial and full thicknesslesions.

It is yet another object of the invention to provide an allograftimplant which facilitates growth of hyaline cartilage.

It is an additional object of the invention to provide a cancellousconstruct which is treated with chondrogenic stimulating factors.

These and other objects, advantages, and novel features of the presentinvention will become apparent when considered with the teachingscontained in the detailed disclosure along with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the anatomy of a knee joint;

FIG. 2 shows a schematic mosaicplasty as known in the prior art;

FIG. 3 shows an exploded perspective view of the inventive two piececancellous construct;

FIG. 4 shows a top plan view of the two piece allograft cancellousconstruct assembly showing the blind bore and plurality of through goingbores in phantom;

FIG. 5 shows a side elevation view of the two piece construct shown inFIG. 4;

FIG. 6 is a side elevation view of the two piece construct of FIG. 4turned 90° with the blind and parallel bores shown in phantom;

FIG. 7 shows a perspective view of the base member of the cancellousconstruct with the cap member removed;

FIG. 8 shows a perspective view of the cap member of the cancellousconstruct;

FIG. 9 is a side elevation view of the cap member shown in FIG. 8; and

FIG. 10 is a side elevation view of the cap member of the construct ofFIG. 9 turned 90°.

DESCRIPTION OF THE INVENTION

The term “tissue” is used in the general sense herein to mean anytransplantable or implantable tissue, the survivability of which isimproved by the methods described herein upon implantation. Inparticular, the overall durability and longevity of the implant areimproved, and host-immune system mediated responses, are substantiallyeliminated.

The terms “transplant” and “implant” are used interchangeably to referto tissue, material or cells (xenogeneic or allogeneic) which may beintroduced into the body of a patient.

The terms “autologous” and “autograft” refer to tissue or cells whichoriginate with or are derived from the recipient, whereas the terms“allogeneic” and “allograft” refer to cells and tissue which originatewith or are derived from a donor of the same species as the recipient.The terms “xenogeneic” and “xenograft” refer to cells or tissue whichoriginates with or are derived from a species other than that of therecipient.

The present invention is directed towards a cartilage repair constructconstructed of two separate pieces of allograft cancellous bone.

Both pieces of the two-piece allograft construct are to be derived fromdense cancellous bone that may originate from proximal or distal femur,proximal or distal tibia, proximal humerus, talus, calceneus, patella,or iliium. Cancellous tissue is first processed into blocks and thenmilled into the desired shapes. The top piece or cap member issubstantially demineralized in dilute acid until the bone contains lessthan 0.2% wt/wt residual calcium. Subsequently, the resultant tissueform is predominantly Type I collagen, which is sponge-like in naturewith an elastic quality. Following decalcification, the tissue isfurther cleaned and may also be treated so that the cancellous tissue isnon-osteoinductive. This inactivation of inherent osteoinductivity maybe accomplished via chemical or thermal treatment or by high energyirradiation. In a preferred embodiment, the cancellous cap member istreated with an oxidizing agent such as hydrogen peroxide in order toachieve a non-osteoinductive material. The bottom piece will be formedfrom mineralized cancellous bone or partially demineralized cancellousbone.

The two piece allograft cancellous construct 20 has a base member 22with a cap member 30 which is held fixed in place in the base member bya pin 40. The base member 22 is preferably constructed of mineralizedcancellous bone and is shaped in the form of a cylinder for easyinsertion into bores cut into the patient to cut away cartilage defectareas. However, the base member 22 may be surface or partiallydemineralized or contain a region of cortical bone so that it iscortical/cancellous. The body of the base member 22 defines a blind bore23 which holds the stem 36 of the cap member 30. The bottom surface 24of the blind bore as seen in FIGS. 5-7 has a plurality of longitudinalthrough going bores 25 extending through the base member 22 and endingon the distal end surface 26 of the base member which is preferablyplanar. The top surface 27 of the base member 22 is also preferablyplanar forming a seat for the cap member 30. A transverse bore 28extends through the diameter of the cylindrical base above the bottomsurface 24 of the blind bore 23 and intersects the blind bore 23. Asecond plurality of through going bores 29 are circumferentiallypositioned around the blind bore 23 parallel to the central axis of thebase member 22 and extend from the top surface 27 to the bottom surface26. The through going bores 25 and 29 have a smaller diameter than theblind bore 23 with a diameter ranging from 0.5 to 2.0 mm

The cap member 30 has a cylindrical top section 32 which has a thicknessof about 3 mm with a top planar surface 33, an outer curved wall 34 anda bottom planar surface 35 which is seated adjacent the top surface 27of the base member 22 when the components are mounted together. The topsurface 33 while preferably planar may be milled to a degree ofcurvature that makes the implant construct match the physiologicalcurvature in the knee. Larger constructs may have a cap member that hasmultiple stem sections and a base with an inverse “female” pattern whichreceives the stem sections. An integral cylindrical stem 36 extends awayfrom the bottom planar surface 35 a length which is not longer than thedepth of the blind bore 23 and has a diameter equal to or less than thediameter of the blind bore 23. The stem 36 defines a transverse throughgoing bore 37 which is aligned with transverse bore 28 of the basemember to receive a cylindrical pin 40 which is inserted radiallythrough the construct to hold the cap member 30 in place within the basemember 22. The cap member 30 is preferably formed of demineralizedcancellous allograft bone with a calcium content less than of 0.2%calcium or has a substantially demineralized region such as the entiretop section with a calcium content less than 0.2% calcium. Thecylindrical pin 40 is preferably constructed of cortical bone and has alength equal to or less than the diameter of the base member 22. The pincan also be constructed of a synthetic material.

The cap member 30 can be secured to the base member 22 by a staple,suture, press fit or an adhesive compound such as fibrin based glue.

The construct 20 is placed in a defect area bore which has been cut inthe lesion area of the bone of a patient with the upper surface 26 ofthe cap member 30 being slightly proud, slightly below, or substantiallyflush with the surface of the original cartilage remaining at the areabeing treated. The construct 20 has a length which can be the same asthe depth of the defect or more or less than the depth of the bore. Ifthe construct 20 is the same as the depth of the bore 60, the base ofthe implant is supported by the bottom surface of the bore and the topsurface 33 of cap 30 is substantially level with the articularcartilage. If the construct 20 is of a lesser length, the base of theconstruct is not supported but support is provided by the wall of thedefect area bore or respective cut out area as the plug is interferencefit within the bore or cut out area with the cap being slightly proud,slightly below, or flush with the surrounding articular cartilagedepending on the surgeon's preference. With such load bearing supportthe graft surface is not damaged by weight or bearing loads which cancause micromotion interfering with the graft interface producing fibroustissue interfaces and subchondral cysts.

If desired, a plurality of through going bores 25 and 29 in theconstruct allow cell migration throughout the construct to promotecartilage growth in the cartilage area and bone growth in the adjacentbore region.

In operation, the lesion or defect is removed by cutting a bore removinga lesion in the implant area. If desired, the open cancellous structureof the cap member 30 may be loaded with a cartilage paste or gel asnoted below and/or one or more additives namely recombinant or nativegrowth factors (FGF-2, FGF-5, FGF-7, IGF-1, TGF-β, BMP-2, BMP-4, BMP-7,PDGF, VEGF), human allogenic or autologous chondrocytes, human allogeniccells, human allogenic or autologous bone marrow cells, human allogenicor autologous stem cells, demineralized bone matrix, insulin,insulin-like growth factor-1, interleukin-1 receptor antagonist,hepatocyte growth factor, platelet-derived growth factor, Indianhedgehog parathyroid hormone-related peptide, viral vectors for growthfactor or DNA delivery, nanoparticles, or platelet-rich plasma. Theconstruct 20 is then placed in the bore or cut away area in an interfacefit with the surrounding walls.

If the construct is moveable within the bore, suitable organic gluematerial can be used to keep the implant fixed in place in the implantarea. Suitable organic glue material can be found commercially, such asfor example; USSEEL® or TISSUCOL.® (fibrin based adhesive; Immuno AG,Austria), Adhesive Protein (Sigma Chemical, USA), Dow Corning MedicalAdhesive B (Dow Corning, USA), fibrinogen thrombin, elastin, collagen,casein, albumin, keratin and the like.

The base of the blind bore 33 of the construct can alternatively beprovided with a matrix of minced cartilage putty or gel consisting ofminced or milled allograft cartilage which has been lyophilized so thatits water content ranges from 0.1% to 8.0% ranging from 25% to 50% byweight, mixed with a carrier of sodium hyaluronate solution (HA)(molecular weight ranging from 7.0×10⁵ to 1.2×10⁶) or any otherbioabsorbable carrier such as hyaluronic acid and its derivatives,gelatin, collagen, chitosan, alginate, buffered PBS, Dextran, orpolymers, the carrier ranging from ranging from 75% to 50% by weight.The cartilage is milled to a size ranging up to 1 mm.

In the gel form, the minced cartilage has been lyophilized so that itswater content ranges from 0.1% to 8.0%, ranging from 15% to 30% byweight and the carrier ranges from 85% to 70% by weight. The particlesize of the cartilage when milled is less than or equal to 1 mm dry. Thecartilage pieces can be processed to varying particle sizes and the HAor other carrier can have different viscosities depending on the desiredconsistency of the putty or gel. This cartilage matrix can be depositedinto the matrix of the demineralized cap member. The putty or gelenhances the tissue integration between the plug and host tissue.

It is also envisioned that demineralized bone matrix and/or growthfactors such as (FGF-2, FGF-5, FGF-7, IGF-1, TGF-β, BMP-2, BMP-4, BMP-7,PDGF, VEGF) or soluble factors such as insulin, interleukin-1 receptorantagonist, hepatocyte growth factor, Indian hedgehog and parathyroidhormone-related peptide, viral vectors for growth factor or DNAdelivery, nanoparticles may be adsorbed or combined with the scaffold orthe cartilage fragments. In another embodiment, platelet-rich plasma maybe added to the scaffold.

It is also envisioned that cells which have been grown outside thepatient can be inserted by syringe into the cancellous cap matrixbefore, during or after deposit of the construct 20 into the defectarea. Such cells include allogenic or autologous, bone marrow cells,stem cells and chondrocyte cells. The cellular density of the cellspreferably ranges from 1.0×10⁸ to 5.0×10⁸ or from about 100 million toabout 500 million cells per cc of putty or gel mixture. This matrix cansupport the previously mentioned chondrogenic stimulating factors.

The principles, preferred embodiments and modes of operation of thepresent invention have been described in the foregoing specification.However, the invention should not be construed as limited to theparticular embodiments which have been described above. Instead, theembodiments described here should be regarded as illustrative ratherthan restrictive. Variations and changes may be made by others withoutdeparting from the scope of the present invention as defined by thefollowing claims:

1. A cartilage repair assembly for repair of a defect in articularcartilage comprising an allograft bone base member and a cancellousallograft bone cap member mounted to said base member, said cap memberpossessing at least one substantially demineralized region.
 2. Acartilage repair assembly for repair of a defect in articular cartilagecomprising a sterile mineralized allograft bone base member defining anaxial bore and a through going bore intersecting said axial bore, ademineralized cancellous allograft bone cap member mounted to said basemember in said axial bore, said cap member being treated to benon-osteoinductive, said cap member defining a through going bore whichis adapted to be aligned with said base member through going bore, saidallograft bone base member being sized to have an interference fit in acut away opening in a cartilage defect area and fastening means insertedthrough said base member and cap member hold the same in a fixedrelationship.
 3. A cartilage repair assembly as claimed in claim 2wherein said mineralized allograft bone base member is cylindricallyshaped.
 4. A cartilage repair assembly as claimed in claim 2 whereinsaid allograft bone base member axial bore is a blind bore with at leastone through going bore running from the base of said blind bore to thedistal end of the base member.
 5. A cartilage repair assembly as claimedin claim 2 wherein said allograft bone base member has a plurality ofthrough going bores running the length of the base member.
 6. Acartilage repair assembly as claimed in claim 2 wherein said cap membercomprises a top disc shaped section and a stem extending from said topdisc shaped section.
 7. A cartilage repair assembly as claimed in claim6 wherein said stem defines a through going bore running transverse theaxis of the stem.
 8. A cartilage repair assembly as claimed in claim 6wherein said cap member top section is cylindrical and is about 3 mm inthickness.
 9. A cartilage repair assembly as claimed in claim 5 whereinsaid plurality of through going bores run parallel to the center axis ofthe base member.
 10. A cartilage repair assembly as claimed in claim 2wherein said cap member is demineralized to a calcium content of lessthan 0.2 percent and treated to remove osteoinductivity.
 11. A cartilagerepair assembly as claimed in claim 9 wherein said bores have a diameterranging from about 0.5 mm to about 2.0 mm.
 12. A cartilage repairassembly as claimed in claim 2 wherein said fastening means is acylindrical pin member mounted in said base member bore and said capmember through going bore.
 13. A cartilage repair assembly as claimed inclaim 2 wherein said fastening means is constructed of allograftcortical bone.
 14. A cartilage repair assembly as claimed in claim 6wherein said cap member top section has a top surface is milled to adegree of curvature that matches the physiological curvature of thecartilage area being repaired.
 15. A cartilage repair assembly asclaimed in claim 2 wherein said cap member contains milled cartilagepieces and a carrier.
 16. A cartilage repair assembly as claimed inclaim 2 wherein said cap member contains one or more additives takenfrom a group consisting of growth factors(FGF-2, FGF-5, FGF-7, IGF-1,TGF-β, BMP-2, BMP-4, BMP-7, PDGF, VEGF), human allogenic or autologouschondrocytes, human allogenic or autologous bone marrow cells, stemcells, demineralized bone matrix, insulin, insulin-like growth factor-1,transforming growth factor-B, interleukin-1 receptor antagonist,hepatocyte growth factor, platelet-derived growth factor, Indianhedgehog and parathyroid hormone-related peptide or bioactive glue. 17.A cartilage repair assembly as claimed in claim 2 wherein on the topsection of said cap member is demineralized to a residual calciumcontent less than 0.2%.
 18. A cartilage repair assembly as claimed inclaim 2 wherein said cap member is constructed with a disc shapedsection having at least a top portion non-osteoinductive and acylindrical shaped stem section extending from said disc shaped section.19. A cartilage repair assembly for repair of a defect in articularcartilage comprising a cylindrical sterile mineralized allograft bonebase member defining a blind bore and a through going bore communicatingwith said blind bore and positioned transverse to a central axis of saidcylindrical base member, an allograft cancellous bone cap memberdemineralized to have a calcium content of less than 0.2 percent andtreated to remove osteoinductivity mounted in said base member blindbore, said cap member including an extended stem which defines a throughgoing bore which can be aligned with said base member through goingbore, said allograft bone base member being sized to have aninterference fit in a drilled bore in a cartilage defect area andcylindrical pin member mounted in said base member through going boreand said cap member stem through going bore.
 20. A cartilage repairassembly for repair of a defect in articular cartilage comprising asterile mineralized allograft bone base member defining a blind bore, atransverse through going bore intersecting said blind bore, a pluralityof through going bores running through said base member parallel to acentral axis of the base member and a demineralized cancerous allograftbone cap member mounted to said base member, said cap member beingtreated to remove osteoinductivity, said cap member defining a throughgoing bore which can be aligned with said bore member bone cartilagecap, said allograft bone base member being sized to have an interferencefit in a drilled bore in a cartilage defect area.
 21. A cartilage repairassembly as claimed in claim 20 wherein said cap member is demineralizedso that it has a calcium content less than 0.2 percent.
 22. A cartilagerepair assembly as claimed in claim 20 wherein said cartilage repairassembly is cylindrically shaped.
 23. A cartilage repair assembly asclaimed in claim 20 wherein said cap member contains one or moreadditives taken from a group consisting of growth factors(FGF-2, FGF-5,FGF-7, IGF-1, TGF-β, BMP-2, BMP-4, BMP-7, PDGF, VEGF), human allogenicor autologous chondrocytes, human allogenic or autologous bone marrowcells, stem cells, demineralized bone matrix, insulin, insulin-likegrowth factor-1, transforming growth factor-B, interleukin-1 receptorantagonist, hepatocyte growth factor, platelet-derived growth factor,Indian hedgehog and parathyroid hormone-related peptide or bioactiveglue.
 24. A cartilage repair assembly as claimed in claim 20 whereinsaid cap member has a top surface that is curved to match thephysiological curvature of the cartilage area being replaced.